The present invention is generally related to a bridge structure with long spans over large water crossing. Known methods for constructing bridge structures over large water crossing have as their objective to reduce the number of the structure supports increasing the length of the span between two adjacent supports. There are two main methods for spanning large water ways.
According to the first alternate method the bridge structure is supported by vertical cables, known as hangers or suspenders cables which in turn are suspended from longitudinal cables known as suspension cables bearing on vertical towers and anchored at their ends. The loads due to the superstructure and design traffic are transferred by the suspension cables to the vertical towers and to the end anchorages. The bridge structure is known as a suspension bridge structure where the main span is the distance between the towers and the side span is the distance between the tower and the anchorage system and there are two side spans.
According to the second alternate method, the bridge structure is supported by inclined cables which in turn are anchored to or supported by the vertical towers, the system being known as a stay cable bridge structure. The loads due to the superstructure and design traffic loads are transferred by the inclined cables to the vertical towers.
The disadvantage of the first method is that the length of the main span is limited to the strength of the suspension cables. When the length of the main span increases the load in the suspension cables and the height of the vertical towers increases. Another disadvantage is that during erection the bridge structure requires additional measures for its stability.
The disadvantage of the second method is that the horizontal component of the force in the inclined cables becomes too big for large structures and can not be taken by the bridge superstructure. Also, the required height of the tower increases with the span length.